In a mobile terminal having a circuit arrangement, different operating voltages are often used in the circuit arrangement. A main supply voltage source, for example in the form of a battery or a rechargeable battery, which is coupled to the circuit arrangement is usually available. This applies not only to mobile radio telephones but also, for example, to portable computers such as laptops, so-called personal digital assistants (PDA), mobile music players, for example MP3 players, etc.
The power reserve of the mobile terminal is, as a rule, a limited resource. Therefore, it is necessary for the circuit arrangement to be as efficient as possible. In order to ensure efficiency, a switching converter, for example a DC/DC converter, for converting the main supply voltage into the different operating voltages is often used to provide the different operating voltages. Switching frequencies of a few kHz to the MHz range for driving the switching converter are selected depending on the design of the switching converter. The problem of switching frequency components and/or their harmonics occurring, as interference signals, in a useful frequency range of the circuit arrangement or in a specially protected system frequency range therefore arises.